package com.innjia.base.utils;

import com.antgroup.zmxy.openplatform.api.internal.util.CoderUtil;

/**
 * 
 * @author xiaoqing.zhouxq
 */
public class Base64Util extends CoderUtil {

    /**
     * Translates the specified byte array into a Base64 string
     * 
     * @param bytes �ֽ�����
     * @return base64������ַ���
     */
    public static String encode(byte[] bytes) {
        int aLen = bytes.length;
        int numFullGroups = aLen / 3;
        int numBytesInPartialGroup = aLen - 3 * numFullGroups;
        int resultLen = 4 * ((aLen + 2) / 3);
        StringBuffer result = new StringBuffer(resultLen);

        // Translate all full groups from byte array elements to Base64
        int inCursor = 0;
        for (int i = 0; i < numFullGroups; i++) {
            int byte0 = bytes[inCursor++] & 0xff;
            int byte1 = bytes[inCursor++] & 0xff;
            int byte2 = bytes[inCursor++] & 0xff;
            result.append(intToBase64[byte0 >> 2]);
            result.append(intToBase64[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
            result.append(intToBase64[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
            result.append(intToBase64[byte2 & 0x3f]);
        }

        // Translate partial group if present
        if (numBytesInPartialGroup != 0) {
            int byte0 = bytes[inCursor++] & 0xff;
            result.append(intToBase64[byte0 >> 2]);
            if (numBytesInPartialGroup == 1) {
                result.append(intToBase64[(byte0 << 4) & 0x3f]);
                result.append("==");
            } else {
                // assert numBytesInPartialGroup == 2;
                int byte1 = bytes[inCursor++] & 0xff;
                result.append(intToBase64[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
                result.append(intToBase64[(byte1 << 2) & 0x3f]);
                result.append('=');
            }
        }
        return result.toString();
    }

    /**
     * ���ֽ���������url safe��base64�ַ���
     * ����+��ת����-, /ת����_, ����ȥ�����ĵȺ�
     * @param bytes �ֽ�����
     * @return url safe��base64�ַ���
     */
    public static String encodeToUrlSafeBase64(byte[] bytes) {
        String normalBase64 = encode(bytes);
        //Step 1, ɾ��ĩβ�ĵȺ�
        int index = normalBase64.indexOf("=");
        if (index > 0) {
            normalBase64 = normalBase64.substring(0, index);
        }

        //Step 2, ��+���滻��-
        normalBase64 = normalBase64.replace("+", "-");

        //Step 3, ��/�滻��_
        normalBase64 = normalBase64.replace("/", "_");

        return normalBase64;
    }

    /**
     * This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
     * equivalents as specified in Table 1 of RFC 2045.
     */
    private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
            'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a',
            'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
            's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8',
            '9', '+', '/'                  };

    /**
     * Translates the specified Base64 string (as per Preferences.get(byte[])) into a byte array.
     * @param base64Str base64�ַ���, ����urf safe���ַ���
     * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64 string.
     */
    public static byte[] decode(String base64Str) {
        //����urlsafe��base64����
        base64Str = toNormalBase64(base64Str);

        int sLen = base64Str.length();
        int numGroups = sLen / 4;
        if (4 * numGroups != sLen) {
            throw new IllegalArgumentException("String length must be a multiple of four.");
        }
        int missingBytesInLastGroup = 0;
        int numFullGroups = numGroups;
        if (sLen != 0) {
            if (base64Str.charAt(sLen - 1) == '=') {
                missingBytesInLastGroup++;
                numFullGroups--;
            }
            if (base64Str.charAt(sLen - 2) == '=') {
                missingBytesInLastGroup++;
            }
        }
        byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];

        // Translate all full groups from base64 to byte array elements
        int inCursor = 0, outCursor = 0;
        for (int i = 0; i < numFullGroups; i++) {
            int ch0 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
            int ch1 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
            int ch2 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
            int ch3 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
            result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
            result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
            result[outCursor++] = (byte) ((ch2 << 6) | ch3);
        }

        // Translate partial group, if present
        if (missingBytesInLastGroup != 0) {
            int ch0 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
            int ch1 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
            result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

            if (missingBytesInLastGroup == 1) {
                int ch2 = base64toInt(base64Str.charAt(inCursor++), base64ToInt);
                result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
            }
        }
        return result;
    }

    /**
     * ��url safe��base64ת����������base64
     * 
     * @param urlsafeBase64
     * @return
     */
    private static String toNormalBase64(String urlsafeBase64) {

        //������еȺ�,˵������urlsafe��bas64,ֱ�ӷ���
        if (urlsafeBase64.indexOf("=") > 0) {
            return urlsafeBase64;
        }

        //Step1, ������Ҫ���伸���Ⱥ�,������ĩβ
        int num = 0;
        int mode = urlsafeBase64.length() % 4;
        if (mode != 0) {
            num = 4 - mode;
        }

        StringBuilder builder = new StringBuilder();
        builder.append(urlsafeBase64);
        for (int i = 0; i < num; i++) {
            builder.append("=");
        }
        urlsafeBase64 = builder.toString();

        //step2, ��-�滻��+��
        urlsafeBase64 = urlsafeBase64.replace("-", "+");

        //step3, ��_�滻��/
        urlsafeBase64 = urlsafeBase64.replace("_", "/");

        return urlsafeBase64;
    }

    /**
     * Translates the specified character, which is assumed to be in the "Base 64 Alphabet" into its equivalent 6-bit
     * positive integer.
     * 
     * @param alphaToInt
     * @return int
     * @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not in the Base64 Alphabet.
     */
    private static int base64toInt(char c, byte[] alphaToInt) {
        int result = alphaToInt[c];
        if (result < 0) {
            throw new IllegalArgumentException("Illegal character " + c);
        }
        return result;
    }

    /**
     * This array is a lookup table that translates unicode characters drawn from the "Base64 Alphabet" (as specified in
     * Table 1 of RFC 2045) into their 6-bit positive integer equivalents. Characters that are not in the Base64
     * alphabet but fall within the bounds of the array are translated to -1.
     */
    private static final byte base64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60,
            61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
            16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31,
            32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
}
